Project Summary Current survival rates of pediatric cancers like leukemia have seen drastic positive response in survival and treatment in the last 20 years. In stark contrast, patients with solid tumor metastasis challenge the current paradigm of intense chemotherapy treatment. Such treatments have failed to change the poor prognosis of metastatic disease indicating a need to understand the complex underpinnings of the in vivo metastatic microenvironment. This need for understanding is enhanced in pediatric patients, where metastasis is promoted by access to a large pool of undifferentiated cells. This project addresses this critical issue in Ewing sarcoma, a cancer that codifies the challenges and shortcomings of current cancer therapeutics. Ewing sarcoma is a malignant cancer of bone and soft tissue targeting children, adolescents and young adults. Overall survival rates for Ewing sarcoma patients with metastasis is abysmal at less than 20% for those with advanced disease and at 60% for those with localized tumors. One in three patients with Ewing sarcoma will have presentation of metastasis. These metrics demonstrate the desperate need to further understand the genesis of metastasis in vivo. This proposal focuses in on the role of the transcription factor SOX6 and its role in Ewing sarcoma metastasis. My preliminary zebrafish xenograft data show a clear, marked increase in metastasis with normal levels of SOX6, while SOX6 shRNA knockdown cells have less or no metastatic spread from injection site. My SOX6 knockdown proteome data show suppression of CAV1, a known gene targeting E-cadherin expression in Ewing sarcoma and increase of BCL2A1, an established anti-apoptotic protein involved in numerous cancer cells. This project?s central hypothesis is: 1) SOX6 mediated protein changes cause an increase in motility and decrease in apoptosis leading to metastasis and 2) that upon metastasis, interaction with the microenvironmental niche triggers invasive proliferative phenotypes mediated by downstream targets of SOX6. These SOX6-mdediated phenotype and proteomic changes support a story of in vivo initiation and persistence of metastatic lesions in Ewing sarcoma. This proposal is the first to look at the intersection of the cell microenvironment with SOX6 to show a new pathway for advancing momentum to targeted treatment of metastasis. Using my unique background in engineering and my training in cell biology, I propose a method that remediates key failures of current treatment by understanding the initiation of metastasis in vivo, persistence of cancer cells, and microenvironmental effects fostering metastasis. This proposal unites many disciplines to offer scientific impact on the genesis of metastasis and provides an incredible opportunity to train my skills as a future independent investigator.